All skin viscose rayon



United States Patent ALL SKIN VISCGSE RAYON Byron A. Thumm, Swarthmore,Pa., assignor to American Viscose Corporation, Philadelphia, Pa., acorporation of Delaware No Drawing. Original application November 3,1954, Serial No. 466,674, now Patent No. 2,853,360, dated September 23,1958. Divided and this application June 24, 1957, Serial No. 667,667

2 Claims. (Cl. 106-165) This invention relates to the production ofshaped bodies of regenerated cellulose from viscose and moreparticularly to filaments and fibers of regenerated cellulose fromviscose.

In the conventional methods of producing shaped bodies of regeneratedcellulose from viscose, a suitable cellulosic material such as purifiedcotton linters, wood pulp, mixtures thereof, and the like is firstconverted to an alkali cellulose by treatment with a caustic sodasolution and after shredding the treated cellulose material, it isallowed to age. The aged alkali cellulose is then converted to axanthate by treatment with carbon disulfide. The cellulose xanthate issubsequently dissolved in a caustic soda solution in an amountcalculated to provide a viscose of the desired cellulose and alkalicontent. After filtration, the viscose solution is allowed to ripen andis subsequently extruded through a shaped orifice into a suitablecoagulating and regenerating bath.

In the production of shaped bodies such as filaments, the viscosesolution is extruded through a spinnerette into a coagulating andregenerating bath consisting of an aqueous acid solution containing zincsulfate. The filament may subsequently be passed through a hot aqueousbath where it is stretched to improved its properties such as tensilestrength. The filament may then be passed through a dilute aqueoussolution of sulfuric acid and sodium sulfate to complete theregeneration of the cellulose, in case it is not completely regeneratedupon leaving the stretching stage. The filament is subsequentlysubjected to washing, purification, bleaching, possibly other treatingoperations and drying, being collected either before or after thesetreatments.

The filaments as formed by the conventional methods, consist of a skinor outer shell portion and a core portion with a sharp line ofdemarkation between the two;

The cross-section of the filaments exhibits a very irregular orcrenulated exterior surface when even small amounts of zinc salts orcertain other polyvalent metal salts are present in the spinning bath.The skin and core portions of the filament represent differences instructure and these different portions possess different swelling andstaining characteristics, the latter permitting a ready identificationof skin and core. The sharply irregular and crenulated surface structurehas a relatively low abrasion resistance and readily picks up foreignparticles such as dirt. Although the core portion possesses a relativelyhigh tensile strength, it has a low abrasion resistance and a lowflex-life, is subject to fibrillation and is relatively stiff.

It has now been discovered that the presence of small amounts ofwater-soluble alkylene oxide adducts of morpholine in viscose and in thespinning bath results in the production of shaped bodies of regeneratedcellulose such as filaments, films, sheets and the like composed of allskin and having improved properties and characteristics providing thatthe amount of the adduct is. maintained with certain limits'and thecomposition ice of the spinning bath is maintained within certancompostion limits which will be defined hereinafter. The most readilydistinguishable characteristics as compared to conventional filamentsinclude a smooth, non-crenulated surface and the filaments consistentirely of skin.

This invention contemplates the use of alkylene oxide adducts ofmorpholine having from 1 to about 50 or more alkylene oxide groups permolecule, preferably from 1 to about 20 alkylene oxide units permolecule of morpholine. It is obvious that for all practical purposesconsidering cost, ease of preparation, commerical availability andsolubility in water, in alkali solutions and in acid solutions, theethylene oxide adducts are preferred.

The production of all skin products requires that certain minimumamounts of the alkylene oxide adduct be in solution in the viscose andin the spinning bath. Therefore, the alkylene oxide adduct must havesuflicient solubility to permit the minimum amount of the adduct to bedissolved in 'both the viscose and the spinning bath. The adduct may beconveniently added to the viscose in the form of a solution in alkali orwater and to the spinning bath in a solution of water or of the spinningbath.

The term adduct is used herein to simplify the disclosure anddescription and in its normal sense designates N-substituted morpholinecompounds formed by the reaction between an alkylene oxide andmot-pholine wherein the alkylene oxide reacts with the amino hydrogenatom to form an addition product or an adduct. Technically, in accordwith accepted terminology for organic compounds, these morpholinederivatives are N-beta-hydroxyalkyl morpholine or N-omega-hydroxyalkylpoly(oxyalkylene)morpholines. The N- designates that the alkylene oxidechain is attached to the nitrogen atom and omega-hydroxyalkyl designatesthat may consist of a mixture of specific compounds, the" averagealkylene oxide content per molecule ofmorpholine being within the statedrange, are satisfactory.

The amount of the adduct which is incorporated in the viscose must be atleast about 0.25% by weight of the cellulose in the viscose and may varyup to about 4%, preferably, the amount varies from 0.5% to 2%. Lesseramounts do not result in the production of products consisting entirelyof skin and greater amounts affect adversely the physical properties ofthe products. Amounts within the preferred range are most elfective inenhancing the characteristics and properties of the products. The adductof morpholine may be added at any desired stage in the production of theviscose such as in the preparation of the refined wood pulp for themanufacture of viscose, before or during the shredding of the alkalicellulose, to the xanthated cellulose while it is being dissolved in thecaustic solution or to the viscose solution before or after filtration.is preferably added after the cellulose xanthate has been dissolved inthe caustic solution and prior tofiltration;

be from about 30% to about 50% based upon the weight of the cellulose.The modified viscose, that is, a viscose containing the small amount ofadduct, may have a salt test above about 7 and preferably above about 8at the time of spinning or extrusion.

In order to obtain the improvements enumerated hereinbefore, it isessential that thecomposition of the spin The adduct The caustic sodacontent may be from about- .3 ning bath be maintained within a welldefined range and that the spinning bath contain in solution at leastabout 0.01% of the adduct. The presence of the alkylene oxide adducts ofmorpholine in the viscose and in the spinning bath combined with theselimited spinning baths results in the production of yarns of improvedproperties such as high tenacity, high abrasion resistance, high fatigueresistance and consisting of filaments composed entirely of skin.

Generically and in terms of the industrial art, the spinning bath is alow acid-high zinc spinning bath to which is added the adduct ofmorpholine in amounts of from about 0.01% to about 0.1%, preferablyabout 0.05%. The bath should contain from about 10% to about 25% sodiumsulfate and from about 3% to about 15% Zinc sulfate, preferably from 15%to 22% sodium sulfate and from 4% to 9% zinc sulfate. Other metalsulfates such as iron, manganese, nickel and the like may be present andmay replace some of the zinc sulfate. The temperature of the spinningbath may vary from about 25 C. to about 80 C., preferably between about45 C. and about 70 C. n the production of the all skin type filaments,the temperature of the spinning bath is not critical, however, as iswell known in the conventional practice in the art, certain of thephysical properties such as tensile strength vary directly with thetemperature of the spinning bath. Thus, in the production of filamentsfor tire cord purposes in accordance with the method of this invention,the spinning bath is preferably maintained at a temperature betweenabout 55 C. and 65 C. so as to obtain the desired high tensile strength.

The acid content of the spinning bath is balanced against thecomposition of the viscose. The lower limit of the acid concentration,as is well known in the art, is just above the slubbing point, that is,the concentration at which small slubs of uncoagulated viscose appear inthe strand as it leaves the spinning bath. For commercial operations,the acid concentration of the spinning bath is generally maintainedabout 0.4% to 0.5% above the slubbing point. For any specific viscosecomposition, the acid concentration of the spinning bath must bemaintained above the slubbing point and below the point at which theneutralization of the caustic of the viscose is sufilciently rapid toform a filament having a skin and core.

There is a maximum acid concentration for any specific viscosecomposition beyond which the neutralization is sufficiently rapid toproduce filaments having a skin and core. For example, in general, theacid concentration of the spinning baths which are satisfactory for theproduction of the all skin products from a 7% cellulose, 6%caustic-viscose and containing the adducts of morpholine lies betweenabout and about 8%. The acid concentration may be increased as theamount of adduct is increased and also as the salt test of the viscoseis increased. There is an upper limit, however, for the acidconcentration based upon the amount of modifier and the concentration ofcaustic in the viscose. All skin products cannot be obtained if the acidconcentration is increased above the maximum value although the amountof the adduct of morpholine is increased beyond about 4% while otherconditions are maintained constant. Increasing the caustic soda contentof the viscose beyond about 8% is uneconomical for commercial productionmethods. For example, a viscose containing about 7% cellulose, about 6%caustic soda, about 41% (based on the weight of cellulose) carbondisulfide, 1% (based on the weight of cellulose) of an ethylene oxideadduct of morpholine containing about 20 ethylene oxide units permolecule and having a salt test of about when extruded into spinningbaths containing 16 to 20% sodium sulfate, 4 to 8% zinc sulfate, 0.05%of the same ethylene oxide adduct of morpholine and sulfuric acid notmore than about 7.8%, results in the production of all skin filaments.Lesser amounts of sulfuric acid may be employed. Greater asaasee amountsof sulfuric acid result in the production of products having skin andcore. A lowering of the amount of adduct of morpholine, the lowering ofthe caustic soda content or the lowering of the salt test of the viscosereduces the maximum permissible acid concentration for the production ofall skin filamenets. It has been determined that the maximumconcentration of acid which is permissible for the production of allskin products is about 8.5%.

The presence of the adducts of morpholine in the viscose and spinningbath retards the coagulation and, therefore, the amount of adductemployed must be reduced at high spinning speeds. Thus, for optimumphysical characteristics of an all skin yarn formed from a viscose asabove and at a spinning speed of about 50 meters per minute, the adductis employed in amounts within the lower portion of the range, forexample, about 0.5%. The determination of the specific maximum andoptimum concentration of acid for any specific viscose, spinning bathand spinning speed is a matter of simple experimentation for thoseskilled in the art. The extruded viscose must, of course, be immersed ormaintained in the spinning bath for a period sufficient to effectrelatively complete coagulation of the viscose, that is, the coagulationmust be sutficient so that the filaments will not adhere to each otheras they are brought together and withdrawn from the bath.

In the production of filaments for such purposes as the fabrication oftire cord, the filaments are preferably stretched after removal from theinitial coagulating and regenerating bath. From the initial spinningbath, the filaments may be passed through a hot aqueous bath which mayconsist of hot water or a dilute acid solution and may be stretched fromabout 70% to about 120%, preferably between and Yarns for other textilepurposes may be stretched as low as 20%. The precise amount ofstretching will be dependent upon the desired tenacity and otherproperties and the specific type of product being produced. It is to beunderstood that the invention is not restricted to the production offilaments and yarns but it is also applicable to other shaped bodiessuch as sheets, films, tubes and the like. The filaments may then bepassed through a final regenerating bath which may contain from about 1%to about 5% sulfuric acid and from about 1% to about 5% sodium sulfatewith or without small amounts of zinc sulfate if regeneration has notpreviously been completed.

The treatment following the final regenerating bath, or the stretchingoperation where regeneration has been completed, may consist of awashing step, a desulfurizing step, the application of a finishing orplasticizing material and drying before or after collecting, or mayinclude other desired and conventional steps such as bleaching and thelike. The treatment after regeneration will be dictated by the specifictype of shaped body and the proposed use thereof.

Regenerated cellulose filaments prepared from viscose containing thesmall amounts of the water-soluble alkylene oxide adducts of morpholineand spun in the spinning baths of limited acid content and containingthe adduct of morpholine have a smooth or non-crenulated surface andconsist substantially entirely of skin. Because of the uniformity ofstructure throughout the filament, the swelling and stainingcharacteristics are uniform throughout the cross-section of thefilament. Filaments produced pursuant to this invention and consistingentirely of skin have a high toughness and a greater flexing life thanfilaments as produced according to prior methods which may be attributedby the uniformity in skin structure throughout the filament. Althoughthe twisting of conventional filaments, as in the production of tirecord, results in an appreciable loss of tensile strength, there isappreciably less loss in tensile strength in the production of twistedcords from the filaments consisting entirely of skin. Filaments preparedfrom viscose containing the alkylene oxide adducts of morpholine'have ahigh tensile strength as compared to normal regenerated cellulosefilaments, have superior abrasion and fatigue resistance characteristicsand have a high flex-life. Such filaments are highly satisfactory forthe production of cords for the reinforcement of rubber products such aspneumatic tire casings, but the filaments are not restricted to suchuses and may be used for other textile applications.

' The invention may be illustrated by reference to the preparation ofregenerated cellulose filaments from a viscose containing about 7%cellulose, about 6% caustic soda, and having a total carbon disulfidecontent of about 41% based on the weight of the cellulose. The viscosesolutions were prepared by xanthating alkali cellulose by theintroduction of 36% carbon disulfide based on the weight of thecellulose and churning for about 2% hours. The cellulose xanthate wasthen dissolved in caustic soda solution. An additional carbon disulfidewas then added to the mixer and the mass mixed for about one hour. Thedesired amount of an ethylene oxide adduct of morpholine was added tothe solution and mixed for about /2 hour. The viscose was then allowedto ripen for about 30 hours at 18 C.

Example 1 Approximately 1% (based on the weight of the cellulose) of anethylene oxide adduct of morpholine containing 1 ethylene oxide unit permolecule (N-beta-hydroxyethyl morpholine or 4-morpholine ethanol) wasadded to and incorporated in the viscose as described above. The viscoseemployed in the spinning of filaments had a salt test of 9.8. Theviscose was extruded through a spinnerette to form a 210 denier, 120filament yarn at a rate of about 22 meters per minute. The coagulatingand regenerating bath was maintained at a temperature of about 60 C. andcontained 7.3% sulfuric acid, 8.2% zinc sulfate, 18% sodium sulfate and0.05% of the ethylene oxide adduct of morpholine. The yarn was stretchedabout 90% while passing through a hot water bath at 95 C. The yarn wascollected in a spinning box, washed free of acids and salts and dried.

The individual filaments have a smooth, non-crenulated exterior surfaceand consist entirely of skin, no core being detecable at highmagnification (e.g. 1500 The filaments of a control yarn spun with thesame viscose but without the addition of the modified agent and spununder the same conditions, exhibit a very irregular and serrated surfaceand are composed of about 75% skin and the balance core with a sharpline of demarkation between the skin and core. Other physical propertiesare set forth in the table which follows the examples.

Example 2 To a viscose as described above, there was added 2% of anethylene oxide adduct of morpholine containing 20 ethylene oxide unitsper molecule (a 4-morpholine poly- (oxyethylene)ethanol). The viscosehad a salt test of 8.2 and was spun into a 210 denier, 120 filament yarnby extrusion into a spinning bath containing 7.6% sulfuric acid, 8.6%zinc sulfate, 20% sodium sulfate, and 0.05% of an ethylene oxide adductof morpholine containing 20 ethylene oxide units per molecule. The bathwas maintained at 60 C. and the extrusion rate was about 22 meters perminute. The filaments were subsequently passed through a hot water bathat 95 C. and stretched about 48%. The yarn was collected in a spinningbox, washed free of acids and salts and dried.

The individual filaments were readily distinguishable from controlfilaments in that they have a smooth, noncrenulated surface and consistentirely of skin while the control filaments have a very irregular andserrated surface and consist of about 75 skin and the balance core witha sharp line of demarkation between the skin and core. Other physicalproperties are set forth in the table which follows the examples.

. I Example 3- As a control for the foregoing examples, aviscosesolution, prepared as described above, having a salt test of 10was spun into a 210 denier, 120 filament yarn by extrusion into a bathcontaining 7.6% sulfuric acid, 8% zinc sulfate and 18% sodium sulfate.The bath was maintained at a temperature of about 61 C. The extrusionrate was about 22 meters per minute. The water bath was maintained at atemperatuer of about 95 C. and the filaments were stretched 82% whilepassing through the hot water. The yarn was collected in a spinning box,washed free of acid and salts and dried.

The individual filaments have a very irregular and serrated surface andconsist of about 75% skin and the balance core with a sharp line ofdemarkation between the skin and the core. Other characteristics are setforth in the table which follows:

Tenacity, Grams per denier Elongation,

percent Skin,

percent Wet Dry Wet Dry Example 1 Example 2 Example 3 (Control) Althoughthe tenacity and elongation are the only properties set forth, they havebeen chosen because of the ease and simplicity with which suchproperties may be determined. In some instances, products made inaccordance with this invention do not exhibit large or greatimprovements in tenacity and elongation, however, the products consistof a smooth-surfaced, all skin structure and possess improved abrasionresistance, flex-like and other properties as disclosed hereinbefore.

One of the properties of viscose rayon which has limited its uses is itsrelatively high cross-sectional swelling when wet with water, thisswelling amounting to from about 65% to about 80% for rayon produced byconventional methods. Rayon filaments produced in accordance with themethod of this invention have an appreciably lower cross-sectionalswelling characteristic, the swelling amounting to from about 45% toabout 60%.

The modifier of this invention may be added to any desired viscose suchas those normally used in industry, the specific viscose composition setforth above, being merely for illustrative purposes. The alkylene oxideadduct of morpholine may be added at any desired stage in the productionof the viscose and may be present in the cellulosic raw materialalthough it may be necessary to adjust the amount present to produce aviscose having the proper proportions of the adduct at the time ofspinning.

The term skin is employed to designate that portion of regeneratedcellulose filaments which is permanently stained or dyed by thefollowing procedure: A microtome section of one or more of the filamentsmounted in a wax block is taken and mounted on a slide with Meyersalbumin fixative. After dewaxing in xylene, the section is placed insuccessive baths of 60% and 30% alcohol for a few moments each, and itis then stained in 2% aqueous solution of, Victoria Blue BS conc.(General Dyestuffs Corp.) for 1 to 2 hours. At this point, the entiresection is blue. By rinsing the section first in distilled water andthen in one or more baths composed of 10% water and dioxane for a periodvarying from 5 to 30 minutes depending on the particular filament, thedye is entirely removed from the core, leaving it restricted to the skinareas.

This application is a division of my copending application Serial No.466,674, filed November 3, 1954, now Patent No. 2,853,360.

While preferred embodiments of the invention have been disclosed, thedescription is intended to be illustraaseegeee 7 tive and it is to beunderstood that changes and variations may be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

I claim:

1. A viscose spinning solution containing from about 0.25% to about 4%,based on the weight of the cellulose in the viscose, of a water-solublereaction product of ethylene oxide and morpholine, the reaction productcontaining from 1 to about 50 ethylene oxide units per molecule ofmorpholine.

2. A viscose spinning solution containing from 0.5% to 2%, based on theweight of the cellulose in the viscose, of a water-soluble reactionproduct of ethylene oxide and morpholine, the reaction productcontaining from 1 to 20 ethylene oxide units per molecule of morpholine.

References Cited in the file of this patent UNITED STATES PATENTS2,125,031 Polak July 26, 1938 2,495,833 Brown Jan. 31, 1950 2,593,466MacLaurin et a1 Apr. 22, 1952

1. A VISCOSE SPINNING SOLUTION CONTAINING FROM ABOUT 0.25% TO ABOUT 4%,BASED ON THE WEIGHT OF THE CELLULOSE IN THE VISCOSE, OF A WATER-SOLUBLEREACTION PRODUCT OF ETHYLENE OXIDE AND MORPHOLINE, THE REACTION PRODUCTCONTAINING FROM 1 TO ABOUT 50 ETHYLENE OXIDE UNITS PER MOLECULE OFMORPHINE.